In recent years, the rise in the speed and efficiency of machining has been in rapid progress. High performance ceramic materials which can cope with this tendency have been desired. For example, titanium carbide exhibits a high melting point and hardness and a low thermal expansion coefficient and shows no drop of thermal conductivity at high temperatures. Thus, titanium carbide is known as a high-temperature material having a high spalling resistance. However, titanium carbide can hardly be sintered. Thus, it has been considered indispensable that titanium carbide is complexed with a metal such as Co and Ni to form a cermet, making it possible to obtain a dense sintered product which can be used for cutting tool, etc. However, cermet has some disadvantages. Since the metals thus incorporated deteriorate the heat resistance of cermet, it can hardly be said that the excellent heat resistance of titanium carbide can be effectively exerted. For example, when used in high speed cutting of an iron-based material of high toughness and ductility, such as ductile cast iron, a cutting tool made of cermet soon comes to an end of its life due to its poor heat resistance.
In order to eliminate these difficulties, a titanium carbide-based ceramic material which comprises a solid solution of a metal in titanium carbide to resist adverse effects at high temperatures and exhibit improved heat resistance has been proposed (JP-B-2-25866 (The term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-62-36065 (The term "JP-A" as used herein means an "unexamined published Japanese patent application")). Although the ceramic material disclosed in the above publications has a good heat resistance, it disadvantageously exhibits a far lower toughness than the foregoing cermet and is liable to chipping.
On the other hand, as a titanium carbide-based ceramic material which exhibits improved toughness while maintaining its good high-temperature properties there has been proposed one comprising silicon carbide whisker incorporated therein (JP-B-8-16028). Although this titanium carbide-based ceramic material exhibits improved toughness due to the incorporation of silicon carbide whisker, it is disadvantageously liable to reaction of silicon in the whisker with iron in the material to be cut, resulting in remarkable deterioration of abrasion resistance when used in cutting of an iron-based material, particularly ductile cast iron.